In the semiconductor wafer production process, patterns to be formed in many layers on a wafer are rapidly becoming finer; hence, the process monitor to monitor whether or not these patterns are formed on the wafer according to designs is increasingly important. Particularly, wiring patterns including transistor gate wiring are deeply associated with their line widths and device operation characteristics; hence, the monitoring of the wiring production process is especially important.
As a length measuring tool to measure the line width of fine wiring on the order of several tens of nanometers, there has been heretofore employed a scanning electron microscope (Critical dimension Scanning Electron Microscope (length measuring SEM)) to measure the line width, the microscope being capable of imaging lines with a magnification factor of several hundreds of thousands. Patent literature 1 describes an example of a length measuring process using such scanning electron microscope. Patent literature 1 discloses a scheme in which based on a local area in an image produced by imaging measurement target wiring, signal profiles of the wiring are added to each other in a longitudinal direction of the wiring to obtain an arithmetic mean to thereby create a projection profile; and the right and left wiring edges are detected in the profile to obtain the distance between the edges, to thereby calculate the wiring dimension.
However, as disclosed in non patent literature 1 (FIG. 1), as for an SEM signal waveform, it has been known that when a shape of the measurement target changes, the signal waveform also changes according thereto. As the semiconductor pattern becomes finer, these measuring errors increasingly affect the process monitor. Non patent literatures 1 and 2 disclose a scheme to reduce such measuring errors. According to the scheme, the relationship between a pattern shape and an SEM signal waveform is beforehand calculated through simulation; by use of its result, there is implemented high-precision measurement not depending on the shape of the target.
Specifically, according to the scheme disclosed in non patent literatures 1 and 2, the relationship between a pattern shape and an SEM signal waveform is beforehand calculated through SEM simulation, to implement, by use of the result, high-precision measurement not depending on the shape of the target. Non patent literatures 1, 2 and 3 disclose a scheme in which a pattern shape is represented by numeric values using parameters and SEM simulation results for various shapes are stored as a library; and the library is compared with an actual waveform, to thereby correctly estimate the shape and dimensions.